Add refrigerator cooling fans

Note this page is more for my own documentation than anything else/ quite long as I kept adding to it. You may find some useful information as to why & what I did, or not. If only using some of the links provided you may gain understanding of your refer- how the drafting in the back affects cooling.

Also just FYI; generally our fridge has capacity of about 40degree cooling lower then ambient temp. The freezer section is designed to be 30 degrees cooler than lower box. So If its 100+ outside unaided lower box easily could see 60, freezer 30. You'll note most state freezer is still cold but main box gets warm. And like us worse as the day goes by. We see inside refer climb in the evening but outside temps dropping. I can only guess due to heat saturation of insulation walls etc. Thermometers that have probe embedded in something give you a better idea of items in refer-monitoring the air just causes grief...

The refrigerator in our camper has never worked all that well. Works to stay in the mid 40s. I have thought for years that Id like to try adding a fan outside the box. Just never did. A recent post on the RV.net forum fella with a pop top was installing a refrigerator in place of ice box. He was asking about the venting/clearances as he would be using side vents. I went and took some pictures of ours, looking down the upper vent to show where chimney stopped from upper vent opening...I saw a fan! Wow even when I had run wires up the wall and over the top of refer on past project-just never stuck my head in there. Fan is located half between upper * lower side vents. Cool i have a fan-guess I don't need another.

GOT fan!
Looking down the upper vent discovered fan

But in the back of my mind the fan puzzled me. If I have a fan, why don't I see temps that other see. Then in another post where a fan was added but closer to the cooling fins and some others posting there mods and results, I decided to go look at ours. Out of curiosity I wanted to see/verify that fan works. On the fins 12v feed goes thru a thermo disk, then to fans. Fan comes on when refer reaches a certain temp. I hooked up jumper bypassing thermo disk, fan didn't come on. Turned on refer, fan came on. So fridge has to be on and thermo disk closed. Wow that fan is loud. I have never heard that since we've owned camper. Bad thermo disk? Set too high.

Went back to the thread about cooling the fridge see if any info on thermo disk. Following discussion about the air movement and how its supposed to work. I visited link to RVmoblie site, article has some basic information that explains how our 'absorbtion' refrigerator works, but more importantly how it vents. Its a main part of the cooling process, its also the main area where installers/camper designers error, by design our side vent are the worst. Basically the hot air rising at back of refer should flow thru the condenser fins at top and out vent.This evacuates the ambient hot air but as it passes thru condenser the rising air also dissipates the heat thru condenser cooling fins.

condenser fins
Condenser fins located at top of refrigerator

With our side mount refer vent and the condenser at very top against fridge, any rising air will simply go out vent, no reason to pass thru fins. Part of the design is that the outer wall should be 1/2 from fins to force air thru fins. Our is 4" plus fins are above vent opening. This is where most are deficient. to much gap. Second would be design of box, just gets hot behind refer, forcing it to work harder. I did identify our factory thermo disk as 158, way too high to be off any benefit.


Heres a diagram of my stock setup and my new one.

So after studying the article at rvmobile the mods and results of others and our current setup, I decided to 1. replace the factory thermo disk so factory fan comes on at a lower temp, 2. add a baffle to force rising air thru the condenser fins before exiting out vent. 3 add some low volume/low amp draw fans to aid in this process, evacuating ambient hot air and aid in heat transfer at condenser fins.

If your fridge wont keep up when its hot or just curious visit this thread at RV.net to see discussion and study this article at RVmobile.com (link no longer valid). Worth the effort to gain an understanding of what might be beneficial. If you camp high heat-refer wont keep up, this might help you decided if a worthwhile project. It would also help following th links to decide if your refer box was poorly executed, and could use some TLC.

Another resource is Dometic http://webspace.webring.com/people/jv/vintage_campers1/Dometic_Refr_Service_Manual.pdf


So that's how I got here. I'm positive it will help. Adding the lower thermo will make factory fan come on sooner should ambient temp to get too high. Adding the baffle, which should increase the passive effect of rising air to cool the fins, and adding fans that will insure air passe thru fins and force air out top vent. .

    On too the install...1st my plan.

A. Add baffle so air flow passively (no fans) will flow thru condenser fins before exiting (as it's suppose to).
B. Change 158 thermo disk with 120. Higher than new fans due to higher amp draw,. want it on last. haven't ordered yet-still debating temp

C... Add new fans. Requires building some sort of mount. These will run thru a 100 thermo button (again not ordered yet).



D..... Wiring : I'm adding an SPDT with center off switch, I will be able to turn on manually or off or to run automatically. . This is where my plan differs from most. The switches will be inside camper. Just convoluted because I can. Switch will send either constant power or power switched by thermo disk thru individual on/off switches for each fan. They will be individual fused with pilot lights, totally unnecessary but I can control the number, which fan(s) on/off and power source of fans. Easily turn off fans at night (factory one still on auto).

Don't think most would want to go to the effort, I enjoy making lil useless otherwise silly stuff out of crap on hand that does something. I'll add some simpler wiring diagram options later.

hmm sounds to simple

    Progress:
1.-order fans (3) 80mm 32cfm 0.1amp muffin fans from newegg ($5ea free ship). Also ordered an interior fan from newegg, same as sold elsewhere for twice as much-cpu hard drive cooling fan, just need to mount (discussed later)

2. Pre run the wires. My switches will be somewhere in front of refer. As there is a 3/4 gap above my fridge I ran from inside across the top to general fan location. (4) #18 ga wires 3 hot & ground) (2) #14 ga wires for power to/ from new thermo disk. . . Constant 12v power is available at front of refer I had added from other project, (otherwise you would access power at refer source in access compartment).
At min I would use a 3 pos switch in back of refer to manually turn on/off or run auto. It is also advisable to grab12v power that is controlled be refer, especially if you have safety kill that cuts power.

3.

3. Hard to see but after roughing in wire I used some closed cell foam, sold as caulk backing, around perimeter of fridge to seal. I had noticed this gap, could see daylight inside when I had done insulation work some time ago. Cool no more outside air. I'm also going to do a bit of caulking in the box. This was needed with or without fan install.

4.

4. In deciding how I might attach deflector at wall, verifying angle enough so vent door doesn't't hit I started seriously looking at how vent frame was attached. As it was loose figured I should recaulk. Hole was is cut in wall, so the sandwich of filon,foam,inner ply exposed. The vent frame really only covers half of foam core. No frame like cabinet door, some black sealant was applied to foam insulation. Metal clips were shoved into foam insulation & the frame screws to them. Nothing stops water from penetrating. .Just a really really bad installation.

I decide to pull vent frame and slip a piece of flashing underneath.This would seal the opening and stop water , also give me something to attach deflector sheet to. This side tracked me quite awhile. Liberally caulked opening, placed flashing reinstalled vent frame with 3" screws into foam, use original angle clips attached to walls to back support top flashing leg.

5.

5. Vent frame reinstalled, caulked a line where frame stops, only covered about 3/4 width of wall foam. Slid it back on so caulk underneath. When set Ill caulk the flashing again so flush to top of frame and water will not pool against flashing. Worked well, pulled frame back tight to wall, wont leak but wasn't part of the plan.

6a.

6a. Fans arrived, cool. I'm building a frame out of 3/4" al angle for fans to set on, was waiting to insure fit. . Measuring 15 times trying to get elevation and checking depth for fans, angle & height of 6" aluminum flashing I'm using for deflector was painful. Got some close numbers then it was cut fit recut fit bend fit drill for about 2 hours. But got it done. End pieces are folded, making an ell, attached to inner side walls and rest against back of outside wall. Using fan to set cross bar depth scribe end pieces, drill hole in end pieces and slotted cross bar for some minor depth adjustment.

6b.

6b. To this frame I'll attach new deflector and at wall. Fans will sit on top of cross bar, screwed at outer corners. Inside edge of fans will simply set against refer wall. I'm attaching foam tape to wall, cover with foil tape to help support but mostly to dampen any vibration. Other than that fans will be hanging. Once cross bar drilled for fans Ill shape angle edge where fans sit so no protrusion into air path. Fans will be centered bout 1 1/2" apart.

7.

7. Had started a small box that will house switches and fuses. Stopped to build fan mount install & wire fans. Ill pre wire as an assembly with a short pigtail. Once mounted Ill connected switch leads to wires I roughed in. If I determine the location I could finished switch wiring...but stopped to focus an fan installation, but mostly cause I'm still not sure where I'm mounting, that and pilot light issue. . The pilot lights I bought are like lasers...really tiny but super bright need about a 1/4 strength. Hopefully as I bought these i can just dim them somehow? That and its looking like something I bout 1965 to add reverb to my blue light 8 track...

8.

8. Finished installing fans on new mount. Finished wiring at back of refer. Had to rethink my original wiring plan and how to use the already pre run wires as I had already sealed up back up refer.. Was going to use 12v power and ground from front of refer that I had added for another project (not part of refer). Had Pre run 2 wires for to/from new thermo and 4 wire cable for fan power & ground.Simple. But realized when I started to wire fans that this would not be part of refer safety cut off circuit. Our fridge power goes thru thermal fuse and disk before entering control board. If very temps are reached (fire) this shuts off refer. Don't think I want fans on if this happens. errr. Well if not for safety circuit org plan would have been a cleaner install. This rethink took most of the day but ended up what most would do if switches inside?.. see diagram.

So the 2 wires I was going to use to /from new thermo disk are now power in constant & from new disk. Ran a fused power wire from after safety thermal connection at board and spliced to pre run wires. I also was going to ground at front of refer but just ran a ground from refer terminal and spliced to fan grounds & the extra wire that was in cable now supplies a ground for interior pilot lights instead of carrying ground from fans. The diagram probably explains it better (see below).

9.

9. Used foil tape to secure wiring to back of fridge-worked well. All connections are soldered & heat shrinked. Had really considered a small terminal block for all connection-but its a fridge. If easy way to attach to back of fridge I would have, maybe even a terminal block with fuses. Though nice easier to just hard wire. If fans need replacing Ill cut at fan. Fairly happy with the install. Just took way too long. Tied raw wires inside together to test fans, wanted to see draw on lower vent. Zip nada, then figured because I haven't made deflector yet fans were just pulling air from top vent, place a couple of magazines against mount. Cool fans drawing air in from lower vent!.

Had scrap of the flashing I'm using for deflector. Very stoked, its going to pretty much be snap in, it will be kinda S shaped nice. When I built mount I added (not shown) four 1" pieces of angle inside to stiffen angle. The flashing slips in between, the bottom in between vent frame clips, pretty tight against added rain flashing-. I will make deflector 2 pieces so I can cut to opening profile and reach .

10.

10. Deflector finished & installed.
Well that was easy. Kinda had an idea this was going to be fairly straight forward the closer I got. But not by design, cause I only had a general idea of what I was going to do. Stuff just started falling into place on its own. I had some 6" aluminum flashing thought might work. When I fixed the vent frame and added the flashing at bottom to keep water out, I inadvertently gave my self a place to attach bottom of deflector. It also gave me more height with the 6" aluminum sheet I had. When I added the stiffeners to the fan mount angle I also inadvertently created a slot that top of deflector could slip into. Realizing all this when I used the scrap to cut match the side profile just was well I couldn't believe it was going to be that easy. I must not be allowing for something.

So I spent a lot of time going over what I was going to do, trying to see the flaw. I had to make deflector 2 pieces to get past the smaller hole than inside dimensions. But I cut the short side, slipped it in,. . Cut the long side. Slipped it in. both pieces set about 1/4 of the bottom but began to think there not going to want to stay, if they slipped down wind thru vent might pop top loose even though it couldn't go anywhere it might get noisy. THen I saw the now unused vent frame clamps. If I put a machine screw thru them with a nut on other side when screw tightened it will clamp the deflector to flashing. Unbelievable. Grabbing 2 screws and nuts the length was perfect. Just plain luck. So the fans are mounted wired and deflector installed. Now that deflectors in, I can really see that is going to help, as the rising air will actually pass thru fins instead of just spilling out vent.

I decided to reinstall the 158 thermo disk on factory fan, I don't really want it going on. With the high temp disk it probably never will with the new fans working. It will serve as a back up. On to finishing pre wiring my switch box, install it and finish inside wiring

11. Finished pre wiring of switch box.


How I finally wired. Looks complicated but not, mapping makes it look so. If you use 12v source after thermal circuit but before it goes into control board should be good to go. What I didn't want to was to put any extra draw on or thru board. If you need to go thru circuit board, have large draw fans, Id use refer to signal a relay and use power from main feed terminal (see suggestions page). What would be considered a large draw?

11.

 

The mini switches and tiny lights difficult for an 80watt 1/2" soldering tip. But got it done like the diagram above.We played with different resistors till we got the brightness of pilot lamps 'just right'. Hooked up to power supply, testing to verify switch functions and pilot lights and overall amp draw of switch box, the fans aren't hooked up.

 

Playing with switches and looking at it box after some thought I concluded I really didn't want the 'power available' red pilot on 24/7 as planned. Its only 60 ma but its 60ma 24/7, . (switches don't control power, refer does, just directs where it goes ). Testing revealed with the SPDT switch really no other way to wire . So I decided to use red pilot to note manually on, the green to note auto on.

 

Actually a better use but requires a DPDT switch. So off again, "goin to the shak". Even more fun soldering the tiny DPDT. Ran jumper from center out pole 1 that's selects what power goes to fans to center pole 2, pole 2 side determines which pilot is lit. So my DPDT switch one side wired 2 source in 1 out to fans, other side 1 source in 2 out to pilots. Rehooked to power supply, played with it for a while. Like it. Rather overkill for what it is

 

Box came out ok but just looked hokey, to hookey to put in camper. Painted the front of box black to give appearance of panel, instead of too much stuff on a wood box.. As removing lights/switches would require un soldering stuff I just masked. Came out ok. I had originally thought of using a panel but all my scrap powered coated alum got buried in the garage somewhere, to lazy to dig out, didn't want raw alum so convinced myself matching wood would blend bette. Out there somewhere is also all my plastic project boxes. Id look if dong this again, as I had to make a box anyway a pre made project box. available in all kinds of sizes radio shack etc. would have worked well.

 

At any rate its done, kinda fun figuring it out, playing with resister values to dial in light brightness. Learning a bit about how our refer works. Reworking wiring to accomplish, well in all reality an exercise in just something to do. I'm actually hoping fans wont be needed with the deflector addition. You'll note 4 lamps consumption is under 0.1 amps @ 12.4v. I though the resistors excess power was spent as heat but...good thing. With all 3 fans on I should be ~-0.4 amps (0.1 amp per fan, 0.1 for all pilot lamps). So under 1/2 amp max because its hot outside-means sunlight so solar is easily putting it back.

11.
12.

12. -Mounting & hooking up switch box. Section of white wall (never understood why it wasn't wrapped at top) is where I was going to mount box after deciding front of refer wasn't going to work. Built the switch box to fit this area, house switch & pilots and cover the white corner..

But after some thought, didn't think we wanted it facing the dinette. Wih some holding up the box & eyeballing, though it looked nice covering up the extra white, we decided to face outward toward stove/ center aisle...However it made the white area a skinner stripe-just looked funny. Then I though if I wrap the corner I could mount box facing outward s and still cover the exposed white wall. Cool

Wow like it, should have done this before. On top of the fridge the stick out had a piece of paneling on top. Just an open area. I pulled the paneling off to run wires. No reason at all, non structural, cant see it, not open to anything. I may cover with a piece of luan or something but save the paneling.

Anyway was the same width as top of slide trim so made this easy.

Finally, installed the box hooked up wiring form switch box to pre run wire. Side of the box the side paneling is just stuck on with small blobs of glue. Underneath it are 2 1/4" holes thru the 1/2x1 1 /2 frame to reach 2 screws that screw it to wall. Killed about 3 days playing with this project. Tucked in the wiring, closed up refer access panel.

And the test..Huh? what the..
Turned on the fridge, turned on the fan 'ON' switch.... huh cant see it-crap bulb burnt? Turned on the fan switches-there barley glowing, its getting dusk in the daylight you wont be able to see. My heart sank. Started thinking bout it I figured since I set up in shop the added wire on refer was too much for the resistors I used. No way I removing the box & rework

Got the ladder out and checked fans. Great at least they are working, pulling a bit of air from sides but still pushing thru fins and as important creating a draft from bottom.

Margaret came out, she liked the box location and how it turned out. She didn't like the unwrapped area on the wall but had never said anything, hmmm 10 years later. I asked what she thought of the lights, she had helped decide on the resistors to use to dim them. She said they looked good, how are they on, I said they are on...to which she replied...oh.

13. -Shut everything down and started picking up &, gathering up tools, then I sat on the dinette. Why is it when projects get a lil involved but your able to surprisingly get er done it'll be the last lil detail, even if non functional that can cause grief. One last look to see how bad this is going to be, I mean I can really tell by switch position what's on though defeats the point of the pilots and the time spent making it work.

Doh!
I turned on the fridge power selector switch. I have a 3 way switch from previous addition that selects source power to fridge, off, direct from battery or from battery thru relay that's is controlled by truck ignition. Realizing it was late and solar panel is no longer generating after selecting battery power, I turned on the fridge but selected 110v even though not plugged in so 12v heater wouldn't come on. WOW fan lights are on and BRIGHT. Hokey smoke what a dummy..It me like a ton of bricks

Ran in to the house Margaret works! " how'd you fix?" she asks. I turned off the fridge, she looks at me puzzled, I explained-the fans and switches are powered off the wire that comes from safety circuit and goes to 12 v heater, When the fridge is on heater it's drawing 17 amp on that wire, the resistors (remember the fans were unaffected) are reacting to the voltage drop. So its not a problem because there is no reason for the fans to be on while in 12v mode. Went from failure to non issue.

Though a bit less brighter than planned, shop 12v power supply I use is actually 13.2 volts, so I should have used just a tad numerically lower resistors.But were good.

Next day with full sun on panels I tested all this, I also verified actual usage of new fan setup. With all fans & pilots lit using approx. 0.3amps over 0.5 standing out put of solar. Solar meter measures battery volts also shows charging rate, glancing at meter when load is added, how much it rises gives a pretty close number of actual amps used, not its function but gives a relative idea.When refer turned on to gas/110v mode, meter rose to 1.3 amps. (0.5 current charge rate + 0.3 for fans & pilots+ 0.5 for refer control board). Excellent. So Fans work no great extra load added. The real test will be actually running when its hot, and watching the internal fridge temps. Still haven't ordered the thermo disk for auto side, its a looped wire at the moment. Ill hook up and run refer and borrow a heat gun to get some temp ideas. Probably 100 if mounted up on the fins but I'm thinking possibly on chimney to cause fans to cycle more with actual firing up. Not sure.need some real numbers; thermo to high fans will never cycle on auto, to low they'll run continuously../

When this done and some real world results Ill update this.

Update 1

. I was getting quite a bit of air being pulled in& turbulence between fans at front of fans, (pulling air back in that's being blown out). With cover on the bottom louver air was actually being drawn in. Thought about adding something between fans sealing the gap but this would block passive air rising. Tried several things, on was adding some side/fins out of paper. this worked really well but would be a lot of work making out of metal. (Had I known easily could have made some simple boxes/tubes to extend intake further down. Might have mounted fans side by side, could have use a simple square between to baffle intake. Finally tried piece of masking tape across exposed front facing side of fans as that's where most of air was being drawn in. This stopped most of the air, though they still draw a bit from between fans, but not disrupting flow. Didn't realize how much side air these pulled otherwise I could have made some baffles or sides. So I guess on the side mount vents fans should be below deflector to draw air from below.

My fix was that fans should have been mounted under neath angle instead of top (lower than top of deflector). But I didn't want to remove and remount so I added another piece of Z flashing to block where air was pulled in. Pic is deceiving ,z is mounted to angle, top leg is in against fans. This worked. FIring up a big smelling smoker (cheap cigar) and blowing smoke In the bottom vent and watching it roll out top vent even the bottom louver, was my reward.

Because I'm only guessing on temp range for thermo button (still haven't ordered) and where best place would be I picked up a small IR thermometer. Every time I go to Harbor Freight with the intention of getting one I end up stocking up on consumable s and other stuff but this time flipped on the blinders and turned off the crap magnet. Got a cool lil thermometer (and not too much other stuff). Will set up some kind of repeatable sequence, measure temps over good part of the day, elect 12v & gas. Get a direction for thermo button and best place for it. Splice into wire loop done. Heres some simpler wiring diagrams and other options Fridge fan options.

Another option this fella is making some prefab kits, small side out of home work but offers fan, thermo, instructions and a plenum for fan. http://www.snydersrvrefrigeration.com/page1.php. Though I noted the site that linked me to snyders had since removed the plenum...

Simpler project Add interior fridge fans
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